BSPP News 31 Autumn 1997 - Online EditionThe Newsletter of the British Society for Plant Pathology
Number 31, Autumn 1997
People and Places (continued)
On 1st August 1997, a new School of Biology was established at the University of Nottingham to incorporate the Life, Agricultural and FoodSciences. This has provided increased opportunities for the expansion of bothresearch and teaching in plant pathology and regular research discussionmeetings in fungal biotechnology and the plant sciences are occurring withinthe School.
The teaching of specialist Plant Pathology modules continues to attract increasingly large numbers with over 35 students registered on all the finalyear modules and more than a dozen students opting to undertake their research projects in this field. On the research front, Paul Dyer has received a BBSRCDavid Phillips fellowship to investigate the physiological and molecularcontrols of sexual reproduction in plant pathogenic fungi with the aim ofdevising new strategies of disease control by interfering with the reproductivecycle. Initial studies will use Tapesia and Fusarium species as well as model saprotrophs.
Within the past year, PhD students have commenced research projects in a number of areas ranging from assessing the potential of using Trichoderma species to control pathogenic Ganoderma species in the tropics supervised by John Peberdy, toprojects looking at Mycorrhizal fungi in biological control on tomato as a model system and also the molecular pathology of Colletotrichum postharvest pathogens on tomato - supervised by Matt Dickinson and Steve Rossall.
Links have also been established with IACR Long Aston (Paul Bowyer, JohnLucas) and IACR Rothamsted (Geoff Bateman) to enhance molecular and fieldinvestigations of the cereal eyespot diseases T. yallundae and T. acuformis, and jointly supervised students registered at the University areundertaking projects at Rothamsted (with Geoff Bateman) and also at NIAB (withWendy Cooper).
Amongst the goings, Anatolia Mpunami, a PhD student working on the coconutlethal disease phytoplasma, supervised by Phil Jones at Rothamsted and MattDickinson, has successfully completed her PhD and returned to the National Coconut Development programme in Dar-es-Salaam, Tanzania. On the comings, Dr.Rosie Bradshaw from Massey University, New Zealand, will be visiting on sabbatical leave from September, comparing strain variation in UK and NZpopulations of Dothistroma pini, a pathogen of pine needles andassessing the possible importance of the sexual cycle in field variability.
Dr Jim Heale and Dr Brian Bainbridge have worked collaboratively in various Plant Pathology projects with a strong molecular biology focus. We have just completed programmes involving studies on population diversity in severa ldifferent plant pathogenic fungi using various DNAfingerprinting methods, aswell as in some cases, sequencing of part of the rRNA gene. These projectsinclude the following pathogens and hosts:
Verticillium alboatrum attacking hop, lucerne (alfalfa) andother hosts, (with Dr Alison Griffen). Analysis of rDNA and mtDNA RFLPs, aswell as RAPDs, showed that the lucerne isolates (all from USA, France and UK)clustered in a single group of clonal origin; most hop isolates were in a largecluster with a few isolates from other hosts, but diversity was revealed byRAPDs. One avirulent lucerne isolate, and two atypical hop isolates, formed twofurther groups respectively, possibly representing divergence at the species level from V. alboatrum.
Verticillium longisporum comb. nov. (with Dr. VassilikiKarapapa). This species attacks oilseed rape and other Brassicas in manyEuropean countries including France, Germany, Sweden, as well as in Japan. Itwas recently recorded in California infecting cauliflower, but it has not yet been found in the rape crop in the UK. The novel findings from this study have led to the renaming of this neardiploid fungus as a separate species, V. longisporum, rather than as it was previously known: V. dahliae var. longisporum (Stark, 1961). Further, its hybrid nature was revealed by RAPD analysis of strains of V. alboatrum (V.aa), V. dahliae (V.d.) and V. longisporum, which showed that several bands specific to either V.aa or V.d. were both present in V. longisporum.
Previous studies in this lab have shown that this neardiploid, vascular wilt pathogen will attack a range of Brassica crops by experimental inoculation, including Chinese cabbage, cabbage, Brussels sprouts, swede and Japanese radish. Arabidopsis thaliana was also tested and at least one, clearcut resistant ecotype was detected. We plan to continue this line of work.
Fusarium moniliforme var. subglutinans, attacking pineapple in Brazil (with Dr. Eduardo Neto); here, population diversity has been investigated and the relationshipbetween anamorph and the accepted teleomorph, Gibberella fujikuroi, as well as to the nonpathogenic F.moniliforme, has been clarified.
Fusarium oxysporum niveum (Fon), attacking watermelon inCyprus. This is an external London University Ph.D. programme with Jim Heale asExternal Adviser to the postgraduate student, Mr Constantinos Poullis, of theDepartment of Agriculture, Cyprus. The project has resulted in the discoveryof Fonresistant rootstocks onto which are grafted otherwise susceptible scionsof watermelon cvs such as `Crimson Sweet' which then yield heavily, with nosigns of disease (see photo). Further, an extra crop is obtained around 8 weekslater, after the first crop is cut back at harvest, even though the graftedrootstocks are planted in Foninfested field soils.
Commercial exploitation of the grafted watermelon rootstocks has already been achieved in Cyprus, replacing virtually all nongrafted plantings, andexport of grafted seedlings to other countries such as Lebanon is underway. Molecular studies on the fungus and inoculation of differential lines haveindicated that Race 2 of Fon is the main cause of heavy disease losses inCyprus as elswhere, and the grafted rootstocks are fully resistant to this andto Race 1.
Healthy watermelons growing in afield in Cyprus infested with Fusarium oxysporum niveum. The plants are grafted, growing on resistantrootstocks discovered by Constantinos Poullis and Jim Heale at King's College,London
A major and continuing research programme in our lab since 1991 has concerned Fusarium oxysporum f.sp. ciceris (Foc) attacking chickpea in Spain, Italy, India and N.Africa. This has been initially funded by the EU as an `ECLAIR' project, for 4years with partners in Spain (Univ of Cordoba, and a Seed Company, Koipesols.a., Seville) and Italy (E.N.E.A.). Dr. Andy Kelly worked on this project forthe first 4 years as a postgraduate.
During '93'94, we were joined by Dr. Antonio Llobell from the Univ. of Seville, who further extended the project to Didymella (Aschochyta) rabiei, causing `blight' ofchickpea. More recently, Dr. Mariola Pedrajas (Univ. of Cordoba), has worked onFoc in our lab as a Spanish Research Council Fellow and is with us until April1998.
This longterm project has resulted so far in molecular probes and primers todetect the two major pathotypes of Foc, viz. `yellowing' and `wilting'respectively. Further work led to the specific detection of the wilt pathotype in planta using inoculated but asymptomatic chickpea plants. Incollaboration with Prof. Diaz's group in Cordoba, almost all known races of Foccan now be detected in vitro by specific PCR. The project has beenrecently advanced by Dr Pedrajas in this lab. by successful detection of thewilt pathotype in soil, and in the next 8 months she will attempt todistinguish between the different races of Foc, in soil, as well as in planta.
"Change and decay* in all around I see" (H F Lyte,Abide with me)
The Plant Pathology and Chemistry Departments have amalgamated to become,surprisingly, the Chemistry and Plant Pathology Department! Dr JeremySweet continues as Head of Dept. The molecular plant pathologists, Drs WendyCooper and Emily Blakemore, are now part of the new Applied TechnologyDepartment, where they will continue research on molecular approaches tothe diagnosis of seed-borne diseases. Wendy Cooper remains Head of theMolecular Biology Section.
Dr Jane Thomas, Head of the Broad-leafed Crops, Herbage and (now)Seed Pathology Section (a prize for a shorter name?), has assumedresponsibility for NIAB's seed health testing programmes. She travelled toPoznan, Poland for the 11th meeting of the International Organisation ofBiological Control (IOBC) group on Integrated Control in Oilseed Crops. Shepresented a paper and poster on assessment of resistance to light leaf spot andstem canker in oilseed rape cultivars. Dr David Kenyon joined Jane Thomas's Section in July from SAC Auchincruive, where he had been working on Rhododendron powdery mildew.
Dr John Hutchins has transferred within NIAB, having been promoted to a new post of Seed Technology Consultant in the Seeds Department. He will be involved in NIAB's internationalconsultancy and training, mainly in plant variety testing and protection, seed certification and seed production.
An exciting season for us with much disease in cereal crops, notably a yellow rust epidemic in winter wheat, rampant Septoria tritici and eardiseases also developing after a wet June! Dr Rosemary Bayles attended aEuropean COST meeting at Wageningen in March and visited Dow Elanco in Hannover during June. Rosemary Bayles and John Clarkson both attended the annualcommittee meeting of the UK Cereal Pathogen Virulence Survey (UKCPVS) heldhere in March, as Secretary and Committee Member respectively.
John Clarkson was 'on duty' at a muddy Cereals '97 near Huntingdon and entertained various visitors to NIAB, including Jan Krupski of Antek, Dr RRighelato of BRF International, Czech plant breeders from Selgen Ltd and Japanese scientists from Ube Industries in Tokyo. He also recently organised various disease identification courses for agronomists and field trials staff from agrochemical companies.
* obviously refers to severely diseased plants!
Microbial Pathogenicity Group
Although the waters of this famous spa have long afforded good health,disease is alive and well in our labs. There are usually about 25 researchpersonnel in our Microbial Pathogenicity Group, a dedicated technician and 6academic staff sharing two labs, although probably only 3 of us would berecognised as pathologists.
The research theme that holds us together is mechanisms of pathogenicity and host defences. Understanding disease should provide new targets for rationaldisease control (we tell our sponsors) or rapid, facile tests for diseaseresistance. We believe in a holistic approach employing sound, basic biologythrough physiology, biochemistry, ultrastructure and molecular genetics.
Thanks to a recent complete refurbishment (only the steel skeleton was left)of our once temporary building, we are now in an excellent facility including labs and rooms that we designed ourselves. It was opened officially by Sir Lewis Wolpert in April, 1997 and houses around 35 academics, 44 post-docs, 76post-graduates and 25 core and research technicians. MPG is one of 7 Research Programmes in the Dept of Biology and Biochemistry and overall we achieved grade 5 in the 1996 Research Assessment Exercise.
Plant pathology is about equally divided between temperate and tropical crop species. Cell wall degrading enzymes of Septoria on wheat is a current main interest and one of many collaborative efforts between Richard Cooper and John Clarkson. In this link with AgrEvo UK, we have strong evidence for involvement of a trypsin protease in pathogenicity. John's interests centre on genetics of fungal pathogens but he also works on fundamental aspects of infection of brassicas by plasmodial fungi, including Plasmodiophora brassicae and Spongospora subterranea on water cress. Their work strongly suggests that this group of pathogens are only distantly related to fungi and have an amoebal phase.
The overarching pathogenicity theme allows much overlap and interaction here. For instance human pathogenic amoebae (Acanthamoeba spp. and Naegleria fowleri) are studied by John Beeching, and John Clarkson, with a yeast geneticist, Alan Wheals, currently research Candida albicans.
Fungal interactions are dissected by Alan Rayner's group but in collaboration with Peter Mills at HRI, we are immersed in compost in an attempt to understand how Trichoderma harzianum inhibits Agaricus bisporus in commercial production. Viral infection (as ds- RNA)of A. bisporus is also under investigation by Robin Hicks.
Much of my other work has centred on vascular (xylem-invading) pathogens; recently these have been mostly of tropical crop species on which there is still so much to do. Long- term funding from Unilever on Fusarium wilt of oil palm led to many key findings such as intercontinental spread from West Africa on seed; a method for eradicating Fusarium from seed; pathogen variation (RFLP, VCGs and pathogenicity)which dictates the release of `resistant' lines; development of a rapid test for resistance (8 days rather than 8 months). With PBI, we currently plan to use the rapid test to develop marker-assisted mapping of resistance to F. oxysporum. The recent events in ex-Zaire have prevented easy access to their breeding trials however. Analogously, with CEPLAC, Brazil, we developed a rapid screen for resistance of cacao to Verticillium dahliae. This led to the discovery of four new phytoalexins of which one, remarkably, is elemental sulphur. Man's first fungicide was already being used by plants, it would seem. Current collaboration with Malcolm Hawkesford and Mike Beale at IACR, Long Ashton will extend the work to other species.
External symptoms of Fusarium wilt of oil palm.
Richard Cooper and his colleagues at Bath University have developed a rapid test for resistance to this disease.
There is much interest here on cassava, the fourth most important staple in the tropics. Other than recent progress in the tissue culture lab on in vitro systems for regeneration and transformation, in this lab John Beeching's group with ODA funding are studying postharvest stress responses in roots ; molecular analysis has revealed induction of various typical defence related proteins such as PAL and glucanase.
Richard Cooper among his cassava plants, in a field trial in Java.
This important tropical crop is the focus of several research projects at Bath University.
I am wrestling with the nature of polygenic resistance to bacterial blight(Xanthomonas campestris pv. manihotis). Resistance to this devastating disease is partial and only expressed against low bacterial numbers; adaxial stomatal number and distribution may play a part in field resistance of some genotypes. Nevertheless, cassava can generate an oxidative burst (as H2O2)to match any respectable model, temperate species.
Real synergy in our labs comes from the large group led by Keith Charnley and John Clarkson on fungal pathogens of insects, such as Metarhizium anisopliae. These potential biological control agents form similar infection structures to plant pathogens, use cuticle degrading enzymes(cf. cell wall degrading enzymes) to penetrate hosts and toxins to suppress defences. In this context we have found the cuticle degrading trypsin from M. anisopliae is very similar in characteristics and sequence to the main protease of S. nodorum; M. anisopliae also produces a family of cyclic peptide toxins (destruxins) similar to HC toxin of Cochlioboluscarbonum and a destruxin has been implicated in virulence of Alternaria brassicae. It's a small world for fungal parasites.
Undergraduates in this School now number over 550 a year, with an intake of around 80 in Biology/Applied Biology. The latter includes training placement(s)for one year and I guess many of you will have encountered our students as we were the first (since 1967) to operate the "sandwich" course in Biology. We offer plant pathology lecture courses in Part 2 and Part 3 and a lab course in Part 2. Also pathology is taught to our M.Sc. Crop Protection students who are based at IACR, Long Ashton for this joint degree with Bristol University. As if all this isn't enough, last November John and I took the course to the Institute of Biotechnology, Zhejiang Agricultural University,Hanzhou, China with British Council funding. It was worth it just for the hot, local rice wine with egg floating in it, and the fermented soy curd which was actually sporulating.
The plant pathology group at Oxford now numbers 12 active researchers an done who hides in her office most of the time. Sarah Gurr's group are mainly interested in changes in gene expression during spore differentiation in biotrophic fungi, notably Erysiphe spp. and in signals derived from the host which trigger such differentiation. The molecular work, undertaken by Ziguo Zhang, is in conjunction with Tim Carver at IGER and is courtesy of the ASD/BBSRC initiative. The D.Phil. students are Emily Pryce-Jones (with AgrEvo),Suzanne Baker (CASE student with Adrian Newton at SCRI) and Alison Hall (CASE student with Rhone Poulenc) and they will be joined in October by Beth Stevens who is joining us from NIAB and who will be a CASE student with John Whipps (HRI).
Sarah and Pietro Spanu, a Royal Society University Research Fellow have a new ASD/BBSRC grant to develop DNA-mediated transformation in Erysiphe. Pietro continues to work on the isolation and characterisation of Cladosporium fulvum hydrophobin genes, whilst also searching for pathogenicity mutants.
Molly Dewey retains her international profile by collaborating with colleagues throughout the world (USA, South Africa, NZ, Australia and Wales!)looking at the detection, quantification and localisation of fungi using monoclonal antibodies.
Plant Pathology continues to be taught at both the undergraduate and postgraduate level in Oxford. The undergraduates are exposed to 27 lectures on plant disease given by Sarah Gurr and such invited guests as Ian Crute, Gary Foster and Michael Shaw, whilst the M.Sc. course in Forestry focusses on lectures in Forest Pathology!
In 1976 the fore-runner of UWE (the University of the West of England) moved to an area of farmland about six miles north of the centre of Bristol. As the years here passed, the original institution has grown dramatically (now about23,000 students!) Where the adjoining farm and farmhouse once stood, an industrial estate now stands and we find ourselves at the hub of a rapidly developing commercial and clerical centre, and no longer on a green field site.
Biological Sciences at UWE has always had a strong research focus in the area of Plant Sciences and particularly in studies on host-pathogen interactions. Peter Spencer-Phillips has a number of interests, including the eco-physiology of endophytic bacteria; algal lectins as novel histochemical reagents; and sensors for plant pathogens. The latter is proving to be particularly productive, with grants from industry and the Potato Marketing Board (you can guess the diseases!). However, his true love (ssh! ... don't tell his wife!) lies with downy mildews. His Downy Mildew Research Group of five MPhil/PhD students and postdoc (plus the temporary, but highly valued, addition of a BSPP Vacation Bursary student) is focussing on the research priorities identified in his recent review on the function of fungal haustoria (Adv. Bot. Res. &Adv. Plant Pathol. 24, 309-333). A new MAFF licence has expanded the range of downy mildew diseases to include three tropical cereal crops, with a World Bank grant linked to The Gambia. He is also being kept increasingly busy with co-ordinating the Downy Mildew Workshop at the 1998 ICPP in Edinburgh - offers of contributions from fellow downy mildew researchers welcome (e-mail: firstname.lastname@example.org)!
Steve Neill (strictly an ABA and stress addict) has recently teamed up with John Hancock (a molecular cell biologist) to look at the generation of reactive oxygen species (ros) and their role as components of the signaling cascade that switches on plant defences. Their PhD student, Radhika Desikan,recently attended the 7th Arabidopsis conference to present data relating to NADPH oxidase and ros-induced gene expression in Arabidopsis cultures.
Alan Vivian's research group are working on the molecular basis of host specificity in Pseudomonas syringae pathovars and his recent review of avirulence genes in the March issue of Microbiology has kept him busy supplying reprints. Dawn Arnold joined the group as a Postdoctoral Research Officer after a successful spell working with John Clarkson in our (is it too early to say?) "sister"institution, Bath University, and brought her considerable expertise of PCR technology to the group. Dawn is currently looking at the phylogenetic division among the races of Pseudomonas syringae pv. pisi in relation to the appearance of novel races in the field. Marjorie Gibbon (postdoc, BBSRC), recently returned after the birth of her daughter Katie (congratulations to her and John!) is completing her work on a "non-host"avirulence gene and its curious relationship with a replication region from a native plasmid in Pseudomonas syringae pv. phaseolicola. Caroline Jarvis and Robert Jackson (BBSRC student) are writing up their PhD's, the former on an unusual avirulence gene, which is present in all races of P. s. pv. pisi, but only expressed in a gene-for-gene manner toward pea in another pathovar and the latter on the role of plasmids in virulence of P. s. pv. phaseolicola towards its host bean. Nuria Elamri (a visitor from Libya) is developing specific primers for PCR-based identification of P. s. pv. maculicola strains. Much of this work is in collaboration with John Taylor at HRI, Wellesbourne and John Mansfield at Wye.
Three of Alan's group are going to Pseudomonas `97 in Madrid in September to present posters, including some with our collaborators Satoshi Yamamoto (a recent visitor to the lab. from the Marine Biotechnology Laboratory in Japan) and Jesus Murillo (from the Universidad Publica de Navarra in Pamplona). Alan himself recently visited Dr Stefania Tegli (another recent visitor to Bristol) in the University of Florence with support from the Italian CNR to collaborate on a project involved with host-specificity in P. s. pv. savastanoi.
UWE's Frenchay campus
Overall, we feel that the UWE group make a healthy contribution to Plant Pathology and it is clear that our students at both undergraduate and postgraduate levels find it a stimulating environment in which to pursue their studies.
President : Dr Henry Tribe
Two meetings were held in the Lent Term. Chris Gilligan provided a comprehensive overview of projects being undertaken in the Dept of Plant Sciences at Cambridge in a talk entitled `Recent Developments in Epidemiology and Biocontrol' (21 February 1997). The epidemiological work had the objectiveof developing a coherent theory to explain spatial variation and the dynamicsof botanical epidemics and included scales ranging from a single plant to awhole field. After consideration of the key processes involved, a series of case studies were used to illustrate components of the model. Primary andsecondary infection of take-all, Rhizoctonia solani and Trichoderma interactions, and Sclerotinia minor in successive crops of lettuce provided excellent examples of how variations in disease in the field could be explained. A stern challenge for pathologists has been development of methods to observe andquantify pathogen activity in the soil. Whilst immuno-blotting techniques allow mycelial growth to be monitored, the use of CT scanners and magnetic resonance imaging will surely lead to major advances in understanding pathogen activity in the soil environment.
Rebecca Stratford from PBI, Cambridge presented `Genetic Transformation of Barley to Resistance to Barley Mosaic Viruses' on 28February. Barley yellow mosaic and barley mild mosaic viruses are widely established in the UK and cultivar resistance is often the only practical means of achieving control in barley. Resistance breaking strains of this viruses are known particularly in Japan and recent interest has focused on transgenic strategies to produce novel kinds of resistance. At PBI, resistance to PVY had been achieved by using a coat protein construct inserted into the potato Maris Piper. Transformation of barley has proved to be more challenging but pioneering work by Wan and Lemaux (1994) using spring barley identified embryo bombardment with DNA on gold particles as a suitable technique to achieve transformation. Herbicide and antibiotic resistance markers have been used to identify transformed embryos. Although coat protein mediated resistance to the barley mosaic viruses has been achieved, the challenge remains to insert it into potential new cultivars and hence exploit the benefits on farms.
A series of meetings are being arranged for the Michaelmas Term, further details from Peter Gladders, ADAS Boxworth (Tel: 01954 268230).
This year's MSc Crop Protection students are getting ready to submit their dissertations. This year is unusual in having no one with English as a first language on the course. Mischievous voices have pointed out that there appearsto be nothing in the regulations which says that theses must be in English, but others say it is unwise to infuriate the examiners...
Paul Hatcher is maintaining an interest in pathology as well as entomology and plant ecology, as he seeks to kill dock plants by all available means.Roland Fox retains an interest in the biocontrol area too, through several students: both of pathogens and of weeds by pathogens. Michael Shaw will be supervising a new PhD student jointly funded by MAFF and HDC as part of a large project on Botrytis in ornamentals doubtless mentioned elsewhere in this newsletter. Mike Deadman continues to collaborate in a wide range of projects at home and abroad. Work in cocoa quarantine is as active as ever, with Ann Parker organising (and doing) the day tod ay operations. Collaboration with ODA through NRI continues, with Jeff Peters coordinating a large project on yam. Needless to say, much staff time goes in failed grant applications, but pathology continues to flourish.